INVESTIGATION OF SPIN-LATTICE RELAXATION IN THE EXCITED TRIPLET-STATES OF IMPURITY MOLECULAR-CRYSTALS INDUCED BY THE TRANSLATIONAL MOLECULEMOTIONS AND INTRAMOLECULAR NUCLEI VIBRATIONS

Direct one-phonon processes of spin-lattice relaxation are investigate d in the excited tripler states of molecular crystals in high magnetic fields and at low temperatures. The mixing of the vibrational motions of the nuclei with the translational ones of the molecule is chosen a s the major phenomenon, leading to the coupling between the spin syste m and acoustic vibrations. The angular, field and temperature dependen ces of the spin-lattice relaxation rate for an isotopic impurity in de uterobenzophenone crystal are calculated by the molecular orbitals and atom-atom potential methods.